NA TURIl 



[Diccemukk I 5. 1898 



hour* of the day. I often si-e the liolloin of this dish sprinkled 

 with sji-ds, evidenily ejected by the birds. At present they are 

 the seeiU of the Lauriistinus (I'ibiiniitiii Tiiiiis). 



Rosehill, Falmouth, November 29. Howard Fox. 



Periodic Tides. 



TllK letter of Mr. A. .S. Thompson, in your issue of 

 December 8, .idds further interesting information as to 

 secondary undulations, to that which I sent you in a paper 

 printed in NATtiRE of February 3 last. This paper appears to 

 nave escaped Mr. Thompson's attention, as in it he will find 

 that this subject was investigated on the Swiss Lakes by Duillier 

 in the ijiiddle of the last century, and by Vaucher in 1804. 

 They found that these undulations are common to all lakes at 

 intervals of about twenty minutes. More recent ly the subject 

 was taken up by Mr. Napier Denison on the Great Lakes in 

 Canada, where he found oscillations of three lo four inches at 

 intervals of from fourteen to eighteen minutes ; and by Mr. Bell 

 Dawson during the tidal survey of the Gulf of St. Lawrence, 

 where he found regular minor undulations occurring, in addition 

 to those due to the tides. W. H. WiiEEl.r.R. 



December to. 



Cristatella Mucedo. 



As this very beautiful polyzoon is generally believed to be 

 nearly, if not quite extinct in ponds in the neighbourhood of 

 London, I should like to recoid the fact that on November 19 

 last, I look a fine specimen two inches in length, which is still 

 living. The colony was packed with statoblasts, most of which 

 are now discharged. It was not perfect when taken, and has 

 again divided since it has been in a small aquarium. 



HlCNRY SciIliRREN. 



9 Cavendish Road, Ilarringay, N., December 3. 



The Invention of the Gimbal. 



Wli.l. you or some of your readers kindly inform me, when 

 and by whom the construction of the gimbal was contrived for 

 the first time? Ku.MAr.ttsi' Minakata. 



7 Effie Road, Walhani Green, S.W. 



THE VALUE OF EXERCISE.^ 

 'X'HE value of e,\ercise for the purpose of maintaining 

 ■'■ mots Sana in corpon- sano lias been recognised 

 from the remotest antiquity. Exercise, however, in its 

 entirety seems to be divided into two sections which, 

 though springing from the same cause, have led to dif- 

 ferent results : professional exercise or the training and 

 maintaining of a body of athletes, and what may perhaps 

 best receive the name of domestic exercise. The former 

 appears lo be one of the many instances of what was 

 originally a means of becoming an end. Professional 

 athletics doubtless took their origin in the use of exercise 

 as a means ; the perfect development of body and mind 

 being the end. The huge muscles and small heads of 

 professional athletes show us that the oiiginal means has 

 finally become the end. This result from the point of 

 view of the hygienist must be regarded as grotesque, 

 and to the physician the professional athlete is neither 

 more nor less interesting than the macrocephalic dwarf 

 The fainting and sickness of the over- or under-trained 

 schoolboy, and the insonmia of the over-crammed student 

 are essentially phenomena of the same class, and due to 

 the same cause viz. pathological plethora of some 

 vascular areas, and pathologicil an.cmia of others. 



The use of exercise as a therapeutic agent, as also its 

 use for the maintenance of he.ilth, falls under the second 

 variety. The practice of exercises as part of one's 

 toilette is very old. Any one conversant with the " heil- 

 gymnaslik " (curative exercises) of the present day, 

 let tlicm belong to the systems of I.ing, .Scholt, or 



' " Rcs|.it.-ilnry Kxcrci>c in ihc Trcalliienl of l)i><:.ist." lly H.nrry 

 CnmpUII, M.I)., U.S., K.R.C.P. Pp. viii -e joo. (I.omlon: lioillicre, 

 Tindall, mill Cox, 1898.) 



NO. 1520, VOL. 59] 



Zander, cannot fail to be impressed with their resemblame 

 to the devotional exercises of the devout Mahometan. 

 Although doubtless the positions assumed by the wor- 

 shipper are symbolical of passi\c submission, cringing 

 obeisance, or subjected defiance, the point of interest to 

 the physiologist is that after the performance of these de- 

 votions one experiences a distinct sense of fatigue. Thus 

 by incorporating in his system of devotion actual mus- 

 cular exercise the I'rophet practically prescribed a system 

 of " heilgyn'nastik," and forestalled tlie modern hygienic 

 use of exercise. It would be interesting to know to what 

 extent the exercise part of his devotions may be modified 

 in the case of a Mohametan with iiior/ms cordis. One fact, 

 as will appear from the context, is worthy of notice. The 

 devotional exercises are all performed slowly, and the 

 cliange of posture is gradual. This is doubtless from a 

 religious standpoint reverential, but from a physiological 

 standpoint it prevents the occurrence of breathlessness 

 or palpitation. In the one case which I bad the oppor- 

 tunity of observing (devotion at sunset), the respirations 

 were accelerated by four, the pulse by sixteen per 

 minute by the devotions. This was in .-Nigeria, near 

 Ilammam Kbira, at .m altitude of 2000 feet. This effect 

 might, no doubt, partially be due to psychical influences. 



The modern therapeutic use of exercise is mainly 

 directed lo tbeattainnient of two objects, local or general. 

 The local use of exercises for the strengthening of certain 

 groups of muscles mostly interests the surgeon or the 

 neurologist. The ingenuity of Zander in inventing 

 machines by which .ilmost every group of muscles in 

 the body can both be exercised, and made to do an 

 exactly graduated amount of work, has done much to 

 develope and systematise treatment in this branch of 

 therapeutics. In the case of all muscles, including the 

 heart, an optimal contraction is only obtained when the 

 muscle contracts against an optimal resistance. This 

 optimal resistance varies according to the condition of 

 the muscle. In the case of the local use of exercise it is 

 most important at the beginning of each set of exercises 

 to find the optimal load. The great advantage of the 

 mechanical system of resistance exercises, as compared 

 with the manual method, is that once this optimal load is 

 found it can be maintained constant, or as the condition 

 of the muscle improves can be accurately increased. 

 From this it follows that the work done on each occasion 

 can be measured mathematically. It is impossible to 

 achieve this by band. 



The second object aimed at by the therapeutic use of 

 exercise is the one of most interest to the physician, 

 viz. the production of a general systemic effect. This 

 effect manifests itself chiefly upon the circulatory 

 and respiratory systems. The sweating produced by 

 exercise, although bringing into play the secretory 

 function of the skin, and thus causing the excretion of 

 certain noxious substances, as well as possibly the pro- 

 duction and addition to the blood of an internal secretion, 

 is essentially ii circulatory phenomenon, and will not be 

 further considered here, especially as exercise is, thera- 

 peutically, rarely pushed lo such .m extent as to produce 

 sweating. One of the elTects of exercise upon the respir- 

 atory system is known to evei^' one, viz. breathlessness, or 

 an mcreasc in the depth and frequency of the respiratory 

 movements. This dyspncta varies according to the con- 

 dition of the patient, and the amount or rather aaiteness 

 of the exercise. I'hysiologists are indebted lo Zunt/ and 

 Geppert (PJliii;er s A nhi'>es., xlii. p. 159^ for having added 

 most essentially to our knowledge of this condition. 

 Before the work of these observers the dyspncea attend- 

 ing exercise was held to be due to a diminution in the 

 amount of oxygen and an increase in the amount of COj 

 in the blood ; was, in short, regarded as an asphyxia. 

 This hypothesis was based upon the experimental results 

 of Mathieu and Urbain (" Du Claz du Sang," Archives de 

 P/iys., iv., 1871-72). Zuntz and Geppert, however, showed 



